MENDEL'S LAW. Great interest has been ex cited among biologists by Mendel's law, and his discovery of certain principles of heredity which will prove of much practical value to breeders of plants and animals, and lend a new phase to the theory of heredity and also of evolution, since the results thus far obtained point to dis continuing evolution and the absence of inter mediate forms. Mendel's original paper was published at Brtinn, Austria, in 1865, but was overlooked until De Vries in 1900 published an exact counterpart of Mendel's theory. while Correns and also Bateson hit upon the same law. As stated briefly by Spillman, it is as fol lows: In the second and later generations of a hybrid, every possible combination of the parent character occurs, and each combination appears in a definite proportion of the individuals. A parent character which is fully developed in the hybrid is said to be 'dominant ;' if it is appar ently absent it is said to he 'recessive.' A case in illustration is thus stated by Bateson: "In breeding crested canaries, the kind of crest de sired for exhibition can, according to canary fanciers, be produced most easily by mating crested birds with non-crested, or 'plain-heads,' as they are called. tf it he supposed that the crested character is usually dominant, we have a simple explanation. When crested birds are bred together, a number of birds are produced whose crests arc coarse and stand up. and others
without crests. The latter are the recessives: the former we may suppose to be the pure domi nants." The fact that the hornless breeds of goats will give off some horned offspring is probably due to the feet that they are what Bateson terms `heterozygotes,' under what is usually called 're version.' From the analogy of cattle, it may he anticipated that the hornless form is domi nant. Consult Bateson. Menders Principles of Heredity, with a translation of Mendel's orig inal papers on hybridization (London. 1902).
1Nlendel's more important discoveries are also thus stated by Castle: "(1) His law of domi nance; when, for example. the offspring of two parents differing in respect of one character all resemble one parent, and possess therefore the dominant character, that of the other parent being latent or recessive. (2) In place of simple dominance, there may be manifest in the im mediate hybrid offspring an intensification of character, or a condition intermediate between the two parents; or the offspring may have a peculiar character of their own (beterozygotes). (3) A segregation of characters united in the hybrid takes place in their offspring, so that a certain per cent. of these offspring possess the dominant character alone, a certain per cent. the recessive character alone. while a cer tain per cent. are again hybrid in nature."